In the commercial marketing of beverages, such as beer and soft drinks, it is highly desirable to market such beverages in a manner to enhance consumer acceptance. One of the more common methods of marketing beverages is in containers, such as two piece aluminum or steel cans, which are provided with easy opening tab means of some nature. One such type of easy opening tab means is known as a ring pull type opening means wherein a closed score line is provided in a can end member and a pull tab is secured to the can end member within the boundary defined by the score line by suitable means such as a rivet. In operation, a force is applied to the tab so as to rupture a portion of the score line. Force is continued to be applied and the tab portion of the can end member within the score line is completely separated from the can lid along with the pull tab and rivet. The separated portions are then disposed of in a conventional manner.
Another type of easy opening tab device is known as the stay on tab (S.O.T.) wherein a non-closed score line is provided in a can end member and a force applying means is secured to the can end member at a location immediately outside a portion of the score line by suitable means such as a rivet. In this type of can end member, the force applying means is hingedly connected to the rivet. In operation, a force is applied to the force applying means and through the hinge association with the rivet, this force is applied to the scored tab portion of the can end member to break the score. The continued application of force pushes the scored portion down into the can. The non-closed portion of the score line retains the scored portion with the can end member and the force applying means remains attached by the rivet to remain with the can end member.
The type of container end members discussed above are usually formed from aluminum. In view of the costs associated with the making of aluminum, it is highly desirable to keep the tickness of the can end member to a minimum. Originally, the ring pull type opening means for can end members were manufactured with a rivet formed from the aluminum in the can end member serving to attach the force applying means to the scored tab portion to be removed. An alternative to this structure is found in U.S. Pat. No. 3,195,768 to Bozek and in U.S. Pat. No. 3,404,799 to McNamara wherein the ring force applying means is attached to the tab portion of the can end member within the score line by a plastic rivet integral with a ring force applying means. In spite of the savings to be obtained by making a can end member as thin as possible and the disclosures in Bozek, McNamara and other similar patents, it is still the present practice in making S.O.T. type openings for can end members to form the rivet from the aluminum in the can end member.
The aluminum S.O.T type tab means for aluminum containers are sometimes difficult to open completely. In addition, the force applying means may be separated from the container end member by simply flexing the force applying means several times, normally less than ten times, until it ruptures and is separated from the container end member. If the separated tab is thrown away, it presents an environmental or ecological problem.